The invention relates generally to the field of pallets used to support large volume objects such as drums or barrels, and more particularly to such pallets which are designed to contain liquid spills in a large sump area formed by the combination of four generally vertical walls and a bottom. Even more particularly, the invention relates to such containment pallets having a deck mounted on a peripheral support shoulder extending from the walls above the sump area for support of the drums, where the walls are reinforced by cross members extending above the sump area.
Hazardous liquid materials are often stored in large drums of 30, 55 or 83 gallon capacity, with one or more drums being placed onto a pallet for easy movement by a forklift or hand truck apparatus. Because there is a high likelihood of leakage or spillage of the liquid, containment pallets have been developed which retain any liquid spillage in a large volume sump area. Regulations promulgated by the Environmental Protection Agency require the sump area to retain 100% of the volume of the single largest storage drum to be supported on the pallet, while the Uniform Fire Code requires a minimum sump area volume of 66 gallons. The containment pallets generally consist of four vertical walls and a solid bottom, with some sort of support means to elevate the drums above the sump area. This support means usually takes the form of raised ridges or column members extending upward from the bottom of the sump area or means to support a separate perforated deck or platform above the sump area, either with centrally located support columns or a peripheral support shoulder incorporated on the inside of the walls. An example of a containment pallet is shown in U.S. Pat. No. 4,930,632 to Eckert et al.
Because the storage drums can be very heavy when filled, and because they are often stored in multiples of two or four drums on a single pallet, it is difficult to design a pallet with sufficient strength which has the necessary sump capacity, especially when taking into consideration that the optimum design will have low side walls and a low deck height to make loading and unloading the drums safer and easier. To maximize the volume of the sump area it is desirable to reduce the number of internal support members for the deck, meaning that a peripheral support for the deck is the preferred construction. In those containment pallets having a deck supported on a peripheral shoulder or lip located near the top of the side walls however, the compressive forces tend to push outwardly against the side walls, causing the walls to bow outward and eventually leading to failure of the pallet wall structure. This deflection problem was addressed in U.S. Pat. No. 5,359,955 to Grebenyuk by providing internal supports which extended from the midpoint of each side wall, creating a T-shape in horizontal cross-section. The supports extended from the bottom of the sump area to the top, the supports creating a surface onto which the deck is placed. The problem with this solution is that the supports themselves occupy a large area of the sump area, which means that the side wall height must be increased to compensate for this lost containment volume.
It is an object of this invention to provide an improved containment pallet structure for containment pallets utilizing a peripheral shoulder to support the deck above the large volume sump area, the improvement being the addition of cross members linking opposite side walls, the cross members being relatively thin in cross-section and positioned above the sump area so as not to reduce the volume of the sump area. Any outward movement of the side walls is resisted by the cross members that connect the two opposing walls.